Silicone acetate brake fluid

ABSTRACT

A SILICONE POLYMER USEFUL AS A BRAKE FLUID COMPRISING A POLYMER OF THE STRUCTURE,   RA(E-CO-O-F)B SIO 4-A-B/2   WHERE R IS A MONOVALENT HYDROCARBON RADICAL OR A HALOGENATED MONOVALENT HYDROCARBON RADICAL, F IS SELECTED FROM   -R&#39;&#39;-, -R&#39;&#39;(-R2)-, AND -R&#39;&#39;(-R2)(-R3)-,   R&#39;&#39; IS SELECTED FROM DIVALENT HYDROCARBON RADICALS AND SUBSTITUTED DIVALENT HYDROCARBON RADICALS, E IS SELECTED FROM THE GROUP CONSISTING OF   R-, ROR&#39;&#39;-, R-CO-O-R&#39;&#39;-, R-CO-R&#39;&#39;, RO-CO-R&#39;&#39;-,   R-(O-CNH2N)Z-OR&#39;&#39;-, AND R&#39;&#39;-OH   WHERE R, R2 AND R3 ARE SELECTED FROM MONOVALENT HYDROCARBON RADICALS AND HALOGENATED MONOVALENT HYDROCARBON RADICALS, N IS A WHOLE NUMBER THAT VARIES FROM 2 TO 4, AND Z VARIES FROM 1 TO 4, WHERE A VARIES FROM 1.11 TO 2.02 B VARIES FROM 0.023 TO 1.00 AND THE SUM OF A+B VARIES FROM 2.024 TO 3.00. THE PRESENT INVENTION COMPRISES A PROCESS IN WHICH ANY BRAKE FLUID SYSTEM IS OPERATED USING THE ABOVE POLYSILOXANE POLYMER AS THE BRAKE FLUID.

3,830,744 Patented Aug. 20, 197 4 United States Patent Olhce 3,830,744SILICONE ACETATE BRAKE FLUID Frank'J. Traver, Troy, N.Y., assignor to iGeneral Electric Company Continuation-impart of abandoned applica- NoDrawing.

' 'tion Ser. No..125,397, Mar. 17, 1971. This application I May 29,1973, Ser. No. 364,505

' Int. Cl. C09k 3/00 Us. (:1. 252-78 6 Claims ABSTRACT OF THE DISCLOSUREI A siliconepolymer useful as a brake fluid comprising a polymer 'of thestructure,

where R is a monovalent hydrocarbon radical or a halogenated monovalenthydrocarbon radical, F is selected from R is selected from divalenthydrocarbon radicals and substituted divalent hydrocarbon radicals, E isselected from the group consisting of if if i R, ROR-, RC-O-R', R-CR,ROCR'-,

BACKGROUND OF THE INVENTION The present case is a continuation-in-partof parent case Ser. No. 125,397, filed Mar. 17, 1971, and now abandoned.

This invention relates to polysiloxane polymers and, in particular, thisinvention relates to ester polysiloxane polymers useful as brake fluids.

At the present time, there are no brake fluids presently in the marketwhich have outstanding performance in many brake fluid tests. Thedesirable specifications or ratings in the brake fluid suggested testsrequire the fluid to have a higher equilibrium reflux boilingtemperature and flash point than that of the presently available glycolbased fluids.

The brake fluids presently onthe market are basically polyether glycolswhich vary from case to case, depending on the type of polyether unitsand the number of polyether units in the polymer chain. Such brakefluids are hydroscopic in that they will pick up large quantities ofwater from the atmosphere. Problems are associated with the packagingand handling of such brake fluids since unless extreme precautions areexercised these brake fluids will pick-up large amounts of water fromthe atmosphere due to their hydroscopicity which will possibly result ina brake fluid with poor performance characteristics as well as a brakefluid that may be unsafe because it can cause a failure of the brakes.It is undesirable to have excess water in the brake fluid since it willseparate out at low temperature such as -40 F. Such water may form icecrystals and may cause the brakes to freeze. Further, it is 2 Lundesirable to have large amounts of water in the brake fluid in that atthe high temperatures, which are commonly present in the operation ofautomobile brakes, the water may evaporate to form vapor which mayrupture the hydraulic lines causing failure of the brakes and possiblythe vapor may cause a very sluggish, ineflicient braking action.

It is, thus, desirable to have a brake fluid on the market which picksup a minimum amount of water through bygroscopicity and which iscompatible with the amount of water it picks up from the atmosphere sothat when the brake fluid is subjected to temperatures as low as 40' F.,brake failure does not result. Brake fluids which have exceptionalproperties are disclosed in the present case as well as in theapplications of Frank J. Traver Ser. No. 125,396, filed Mar. 17, 1971,Frank J. Traver Ser. No. 125,398, filed Mar. 17, 1971 and Frank I.Traver, US. Pat. 3,725,287, issued Apr. 3, 1973.

Accordingly, it is one object of the present invention to provide apolysiloxane polymer useful as a brake fluid which has exceptionalperformance as an automobile brake fluid.

It is another object of the present invention to provide an esterpolysiloxane useful as hydraulic fluid for a central hydraulic system.

It is an additional object of the present invention to provide a brakefluid which is only slightly hydroscopic and is compatible with thewater that it picks up from the atmosphere such that the Water will notseparate out either at low temperatures or high temperatures from thebrake fluid mass.

It is yet another aim of the present invention to provide a polysiloxanepolymer useful as a brake fluid which has a high flash point, fire pointand autogenous condition temperature which far exceeds those of priorbrake fluids.

SUMMARY OF THE INVENTION where R is a monovalent hydrocarbon radical ora halogenated monovalent hydrocarbon radical, F is selected from R isselected from the class consisting of a divalent hydrocarbon radical andhydrocarbon substituted divalent hydrocarbon radicals, R and R are.selected from monovalent hydrocarbon radicals and halogenated monovalenthydrocarbon radicals, E is selected from the group consisting of n is awhole number that varies from 2 to 4 and z varies from 1 to 4 where avaries from 1.1 to 2.02, b varies from 0.023 to 1.00, and the sum of a+bvaries from 2.024 to 3.00. More specifically, R' is selected fromalkylene or arylene radicals of up to 20 carbon atoms,

warm

"polysiloxane polymer is obtained by reacting an alkenoic alcohol withan organic acid in the presence of a strong acid catalyst so as toesterify the alkenoic alcohol and then reacting the resulting ester bySiH-olefin addition with a hydropolysiloxane in the presence of aplatinum catalyst.

I It is understood that the present ester polysiloxane can be utilizedin a brake fluid in anyvehicle brake hydraulic system or as a hydraulicfluid in any hydraulic system. Thus, the present ester polysiloxane canbe used as a brake hydraulic fluid in either automobile brake drumhydraulic systems or automobile disc brake hydraulic systems or "othervehicle braking hydraulic systems. Such hydraulic brake systems usuallycomprise an activating means which maybe a brake pedal and the othercomponent that act upon the hydraulic fluid. The brake pedal oractivating means is connected through appropriate hydraulic lines whichcan be referred to simply as hydraulic line means to the mastercylinder. The master cylinder which is present in most vehicle hydraulicbrake systems can also be referred to as reservoir means. Finally, thehydraulic lines "are connected to the disc brake components or brakedrum components in the wheels or other such vehicle wheel componentswhich translate the hydraulic force transmitted through the hydrauliclines into mechanical braking force in the vehicle of a vehicle maysimply be referred to herein as activated means. The invention of themechanical parts of a particular vehicle hydraulic brake system forms nopart of the present invention. The invention of the present case lies inthe process of the use of the ester polysiloxane of the present case inany vehicle hydraulic brake system. Accordingly, any vehicle hydraulicbrake system or any hydraulic system for that matter in accordance withthe present invention will generally comprise activating means,reservoir means, activated means and hydraulic line means connecting theactivating means, activated means and reservoir means, 'wherein all ofsaid means are substantially filled with the ester polysiloxane of thepresent case. Thus, the present invention lies in the process of the useof the ester polysiloxanes of the present case as a brake hydraulicfluid in any 'vehicle hydraulic brake system and the mechanical parts ofsuch brake hydraulic systems which form no part of the present inventionwill be referred to in the specification and claims of the present casefor brevity as activating means, activated means, reservoir means andhydraulic line means connecting said activating means, said activatedmeans and reservoir means.

DESCRIPTION OF THE PREFERRED EMBODIMENT The radicals R, R R and Rappearing in Formula (1) are well known in the art and are typified byradicals usually associated with silicon-bonded organic groups in thecase of R, R R and are generally associated with divalenthydrocarbonradicals in the case of R.

Theorganic radicals represented by R include monovalent hydrocarbonradicals, halogenated monovalent hydrocarbon radicals and cyanoalkylradicals. Thus, the radical Rmay .be alkyl, such as methyl, ethyl,propyl, butyl, octyl; aryl radicals such as phenyl, tolyl, xylyl,naphthyl radicals; aralkyl radicals such as benzyl, phenylethyl,radicals; olefinically unsaturated monovalent hydrocarbon-radicals suchas vinyl, allyl, cyclohexyl radicals; cycloalkyl radicals such ascyclohexyl, cycloheptyl radicals; halogenated monovalent hydrocarbonradicals such as chloromethyl, dichloropropyl, l,l,l-trifluoropropyl,chlorophenyl, dibromophenyl and other such radicals; cyanoalkyl radicalssuch as cyanoethyl, cyanopropyl, etc. Preferably, the radicalsrepresented by R, R R have less than 8 carbon atoms and in particular itis preferred that R, R R be methyl, ethyl or phenyl. The radicals R inthe different hydrocarbon substituent groups in Formula (1) may be hesame or different. The radicals represented by R may be any divalenthydrocarbon radical or polyvalent hydrocarbon radicalsubstituted byhydrocarbon radicals such as alkylene or-lar ylene radicals orhydrocarbon, substituted alkylene orarylene radicals of less than 20carbon atoms such as-methylene, ethylene, various isomers of thephenylene'radicals or substituted phenylene radicals. In thepreferredembodiment; R is propylene. Further, R can be alkylene, hydrocarbonsubstituted alkylene, arylene or hydrocarbon"substitutedal- In thisformula, R is preferablymethyl, x varies from 1 to 10 and y varies from1 to 15.

The compound of Formula (11) may also-have the structural formula asfollows: 2.

0 i O-ii-E where R, F, x and y have the meanings and'values indicatedabove. The most preferred compounds that are useful as brake fluids comeWithin the scope of Formulas (l), (2) and (3) are as follows:

H (IJHa CHI CHaO(CHz)zCOCH CH,CH,SiO $10 :lucnm S1011. Ha H2) H O=C(CHahO CH g SlCHgCHgCHyO C(CHg)gOCH| 1 CH3 CH3 omfo-ocrnomcmsio SiO[(CHahSiOim O=CCHS 5 t sicmcnlcnioc-ons One method for forming thecompounds of Formula (1) comprises the reaction of a compound of theformula CH =CH-'GOH with an organic acid so as to esterify the acidwhere G is selected from Thus, the organic acid may be selected from thegroup comprising ncoorr, ROR'COOH, RiJ-R'COOH,

where R and R' were defined previously and where the substituent groupsR and R' in the organic acid may be the same or diiferent from the R andR substituent groups attached to the silicon atom in Formula (1). Theesterification reaction is preferably carried out in the presence of thecatalyst which may be a strong acid such as sulfuric acid, hydrochloricacid or nitric acid. Preferably, the catalyst is sulfuric acid ortoluene sulfonic acid. Although the reaction may becarried out at roomtemperature, it has been discovered that the esterification reactionproceeds too slowly at that temperature. Preferably, the reactiontemperature is in the range of 50 to 150 C. and more preferably in therange of 70 to 130 C. The reaction is allowed to proceed for 2 to 15hours and preferably from 5 to hours. Further, the esterificationreaction is preferably carried out in the presence of an inert solventselected from toluene and xylene, benzene, mineral spirits and otherinert solvents. After the reaction has proceeded to completion, that is,after the reaction period of 5 to 10 hours, the acid is neutralized withsodium bicarbonate and additional inert solvent is added to the reactionmixture. Then the organic layer is Washed with water and the resultingorganic layer is separated from the aqueous layer that forms. Then theester is distilled from the organic layer by a distillation procedure soas to separate out the pure ester material. In place of theesterification reaction, the organic acid may be reacted with sulfonicchloride so as to give an organic carbonyl chloride product. Thisreaction is preferably carried out at room temperature, that is, 20 to50 C. The reacted acid chloride can then be reacted with analkenyl-alcohol in the presence of a basic media such as ammonia,triethylamine, pyridine, as hydrogen chloride acceptors at roomtemperature, to product the resulting ester compound.

To obtain an ester product with a polyether group therein, the polyetheralcohol of the formula I is reacted with the Na at room temperaturewhere R, n, and z are defined previously. The resulting compound whichhas the formula R(OC H ONa is then reacted with a compound of theformula,

XR -COOGCHCH where X is a halogen, G is selected from and R is adivalent or polyvalent hydrocarbon radical selected from arylene andalkylene radicals of up to 20 carbon atoms and hydrocarbon substitutedalkylene and arylene radicals of up to 20 carbon atoms. The reactionproduct of this reaction is which can now be reacted by SiH-olefininterchange with a hydrogen polysiloxane to obtain the final esterpoly-siloxane. The reaction between the sodium polyether and the halogenolefin may be conducted at room temperature although elevatedtemperatures of 5080 C. is prepared. Further, an inert solvent may beutilized in the reaction although such a solvent is not necessary.

To produce the deired reaction products of the present case, theolefinic ester is then reacted with a compound of the formula,

in the presence of a platinum catalyst, where R has the meaning definedpreviously and a varies from 1.11 to 2.02, b varies from 0.023 to 1.00and the sum of a+b varies from 2.024 to 3.00. Preferably in the aboveformula, a varies from 1.23 to 2.02, b varies from 0.055 to 0.92 and thesum of a plus b varies from 2.074 to 2.5. The hydropolysiloxane is addedto the reaction pot and heated to a temperature in the range of to C. toremove any free water and toluene is then added to the reaction pot. Themixture is heated to a temperature in the range of 100 to 150 C. toremove any free water by toluene-water azeotrope. Once the solution ofthe hydropolysiloxane and the toluene is dried in accordance with theazeotrope technique, a trace of platinum catalyst is added to themixture. Then the ester is slowly added to the reaction pot. Theaddition is exothermic so the temperature is controlled by the olefinaddition rate and is usually maintained in the range of 25 75 C. Duringthe reaction, the SiH peak disappearance is followed by infrared scan.Once the addition of olefin to silicon hydride is completed, thesolution is filtered through fullers earth to remove any precipitates.Then the solution is stripped to remove solvents and low boilingfractions to yield the desired polysiloxane which falls Within Formula(1) and which is the desirable brake fluid .of the present case. By therate of the addition of the olefin, the temperature is able to becontrolled in the range of 25 to 100 C. and, more preferably, in therange of 25 to 75 C. v

A suitable catalyst for addition of organohydrogen polysiloxane to thealkenoic ester or polyether ester are the various platinum and platinumcompound catalysts known in the art. These catalysts include elementalplatinum in the finely divided state which can be deposited on charcoalor alumina, as Well as various platinum compounds such as chloroplatinicacid, the platinum hydrocarbon complex of the type shown in US. Pats.3,159,- 601, 3,159,662, as well as the platinum alcoholic complexesprepared from chloroplatinic acid which are described and claimed inLamoreaux, US. Pat. 3,220,972.

used, the catalyst is generally used in amounts suflicient to provideabout 10'" to l moles of platinum per mole of the ester reactant. Asmentioned previously, the reaction is effected by adding theorganohydrogen polysiloxane to an inert solvent being selected from thegroup of benzene, toluene, xylene, mineral spirits and other inertsolvents. The reaction mixture is preferably heated to 25 to 75 C.before the addition of the alkenoic acid ester. The olefinic ester isthen added to the hydrogen polysiloxane solvent mixture at an additionrate so as to maintain the reaction temperature in the range of 25 to 75C. during the reaction. Preferably, the reaction is allowed to proceedto completion in 4 to 15 hours and preferably in 5 to 8 hours. After thereaction period is over, a sample of the reaction mixture may be checkedby infrared analysis for SiH bonds to determine how far the reaction hasproceeded to completion. When at least 95% of the SiH organopolysiloxanehas been converted to the reaction product, the reaction mixture may becooled and the reaction may be considered to have proceeded to asufficient extent for the conversion of the ester polysiloxane.

In the case where the olefinic ester has free hydroxyl groups, theSiH-olefin addition reaction may be carried out in the presence of abuffer in order for the reaction to properly proceed. Any of thecommonly known buffers may be used to buffer the reaction mixture orsolution containing the hydrogen polysiloxane and the solvent therein,such that the reaction proceeds in accordance with the desiredconditions.

Another method of protecting the free hydroxyl groups in an olefinicester having such free hydroxyl groups is to first react the olefinicester with trimethylchlorosilane such that the trimethylchlorosilaneattaches itself to the free hydroxyl groups. the SiH-olefin additionreaction can then be carried out without any bufier present. After thereaction product has been obtained from the reaction, then thepolysiloxane ester can be subjected to a mild hydrolysis with water or atrace amount of a weak acid can be added to the polysiloxane ester so asto liberate the trimethylsilane group and form hydroxyl units at theterminal position of the polysiloxane ester such that it once again hasfree hydroxyl groups. This method is only used when the ester moiety hasfree hydroxyl groups attached to it so as to allow the SiH-olefinaddition reaction to proceed in the proper manner.

Preparation of the organohydrogen polysiloxane of Formula (5 which cancontain both saturated and olefinically unsaturated hydrocarbon groupsmay be carried out by any of the procedures well known to those skilledin the art. Such polysiloxanes can be produced by following theprocedure involving the hydrolysis of one or morehydrocarbon-substituted chlorosilanes in which the substituents consistof saturated hydrocarbon groups, the crude hydrolyzate containing amixture of linear and cyclic polysiloxanes. Further, one or morehydrocarbonsubstituted chlorosilanes with hydrocarbon-substituentscomprising one or more olefinically unsaturated hydrocarbon groups arehydrolyzed to produce a crude hydrolyzate containing a mixture of linearand cyclic polysiloxanes. The two crude hydrolyzates are polymerized bybeing treated with KOH to form mixtures of low boiling, low molecularweight cyclic polymers mixed with undesirable materials such asmonofunctional and trifunctional chlorosilane starting material. Theresulting compositions are fractionally distilled and there is collectedtwo pure products of the low boiling, low molecular weight cyclicpolymers free of any significant amount of monofunctional andtrifunctional groups. In order to depolymerize the two hydrolyzates,there is added to them a catalyst and the mixture is heated to atemperature above 150 C. to produce and recover byevaporation a productconsisting of low molecular weight cyclic polysiloxanes comprising, forexample, about of the tetrasiloxane and 15% of the mixed trisiloxane andpentasiloxane. The distillate consisting essentially of low molecularweight cyclic dimethyl polymers free of any significant amounts ofmonofunctional and trifunctional groups is collected in the vessel. Thethen dried cyclic siloxane contains less than 50 parts per million ofwater. The cyclic methylvinyl and diphenyl cyclic siloxanes are preparedin the same way. The two cyclic siloxanes are added in the desiredproportions in a reaction vessel so as to be subjected to an equilibriumreaction to form the hydrogenpolysiloxanes of Formula (5). Thus, about2.5 to 17 mole percent cyclic diphenylsiloxane can be added to 83 to97.5 mole percent dimethyl cyclic siloxanes. If desired, and dependingupon the type of compound that is to be produced, 0.1 to 1.0 molepercent of methylvinyl cyclic siloxane may be mixed with dimethyl anddiphenyl cyclic siloxanes or other desired proportions of the cyclicsiloxanes can be used to produce thedesired polymer. To the abovemixture of pure cyclic siloxanes there is added a polymerizationcatalyst such as KOH. The potassium hydroxide breaks a ring of cyclicsiloxane to form'a potassium. silonate, which can then attack othercyclics to break the rings and increase the chain length of thesiloxanes formed. There is further added to the reaction mixture in theamount of one or more monofunctional compounds calculated to function asend-blockers for limiting the degree of polymerization and consequentlythe lengths and molecular weights of the linear polysiloxane chains andfor stabilizing the polymers.

Usually a small amount of monofunctional compounds are added to functionas end-blockers so as to regulate the chain length of the polymers. Thefunctional compounds there may be employed satisfactorily forcontrolling polymer growth include, among others, hexamethyldisiloxane,tetramethyldiethoxydisiloxane, dihydrogentetraethoxydisiloxane,divinyltetraethoxydisiloxane, and deca-methyltetrasiloxane. Theequilibration reaction is carried out from 2 to 4 hours until about 85%of the cyclic diorganosiloxanes have beenconverted to polymerend-stopped with monofunctional groups. When the 85% conversion pointhas been reached, there are just as many polymers being converted tocyclic siloxanes as there are cyclic siloxanes being converted to thepolymers. At that time there is added to the mixture a sufficient amountof an acid donor such as phosphoric acid, that will neutralize the KOHcatalyst so as to terminate the polymerization reaction. The cyclicdiorganosiloxanes' in the reaction mixture are then distilled off toleave the polyhydrogensiloxane which is useful in the present invention.Hydrocarbon-substituted polysiloxanes with pending groups consistlargely of groups other than methyl, such as ethyl or the saturatedhydrocarbon groups and olefinically unsaturated hydrocar'bon groupsother than, or in addition to, vinyl groups can be produced by means ofprocedures similar to those described above or by the means ofprocedures modified in accordance with the characteristics of thehydrocarbon groups to be included.

The above-procedure can be used to produce branchchain polysiloxanes, as.well as linear diorganopolysiloxanes, depending on the reactants thatare used in the equilibration reaction.

An alternate method of producing the hydrogenpolyorganosiloxane of thepresent case which is used in the SiH-olefin addition reaction and whichis represented by the average unit Formula (5), hexamethyldisiloxane isequili brated with octamethyltetrasiloxane andtetramethyltetrahydrogentetrasiloxane in the proper molar proportion, inthe presence of 3% of acid-treated clay, such as 3% acid on fullersearth and the reaction mixture is heated for 5 hours at to C. toequilibrate the reaction mixture. After hours of reaction time, whenapproximately 85% of the tetramers have been converted to the polymerpolysiloxane, the catalyst is neutralized with a weak base and thevolatile cyclics are distilled off to leave a substantially purepolyorganosiloxane. By using dihydrogentetramethyldisiloxane as thechain-stopping unit instead of hexamethyldisiloxane, there can beobtained a linear polysiloxane having hydrogen groups at the terminalpositions of the polymer chain, as well as in the center positionof thepolymer chain. Such a polymer product allows the production of esterpolysiloxanes with the ester groups attached by SiH-olefin additionreaction at the terminal positions of the chain, as well as in thecenter position of the polymer chain.

vBesides the number of other advantages, such as a higher flash point,fire point and auto ignition temperature, as well as much lower waterpick-up than the brake fluids presently on the market, the brake fluidsof the present case have the advantage that they are paintable, thatis,if they are spilled on a portion of the automobile, the .fluid will notstain or remove the paint on the surface with which it comes in contact.This is not the case with standard brake fluids which upon coming intocontact with the painted area in an automobile, will either take thepaint off or stain it so that the painted area has to be repainted. Thisadvantage is especially pertinent for automobile manufacturers where alarge amount of brake fluids are handled and in which cases the brakefluids are quite often spilled on the painted areas of the automobiles.ln thosecases, the automobiles have to be repainted. However, since thefluids of the present case do not affect the paint, the brake fluid ofthe present case can be merely wiped off the painted area without anyeffect whatsoever on the painted area'below.

Another advantage of the brake fluids of the present case is that theyare non-toxic, that is, they do not give off toxic fumes and do noteffect the skin or cause dermatitis of any type or sort. With the brakefluids presently on the market and especially in the case wheremechanics and factory workers have to handle large amounts of brakefluids, it is very often the case that the workers develop some sort ofa dermatitis as a result of contact with the brake fluids.

The following brake fluid tests are the tests recommended for evaluatingthe performance of a brake fluid.

A dry equilibrium reflux boiling point test is carried out by placing 60mm. of brake fluid in a flask and boiling under specified equilibriumconditions in a 100 ml. flask. The average temperature of the boilingfluid at the end of the reflux period is determined and corrected forvariations of barometric pressure, if necessary, as the equilibriumreflux boiling point. The brake fluids of the present case have anequilibrium reflux boiling point of 550 F. or above.

The. next testis the wet equilibration reflux boiling point whichiscarried out by taking a 100 ml. sample of the brake fluid which ishumidified under controlled conditions, then 100 ml. of SAEcompatibility fluid is used to establish the endpoint of thehumidification. After the humidification, the water content and theequilibrium reflux boiling point of the brake fluid are determined as inthe previous test. When our 'fluid is run under the test conditions setforth above, there is'obtained an equilibrium reflux boiling point of342 to 360" F. or greater, depending upon the rate at which the brakefluid is heated. :For the flash point determination, the test is to takea test dish which is filled to a specified level with brake fluid.Thefluid temperature is increased rapidly and then at a slower rate asthe'flash point is approached. At specified intervals, a smalltest flameis passed across the cup. The lowest temperature at which application ofthe testflame causes vapors above the fluid surface to ignite is theflash point. The brakefluids of the present invention have a flash pointof 265 1 and greater.

If some of the volatiles are stripped off from thebrake fluid of thepresent case, the flash point can be increased to exceedingly highertemperatures.

The procedure to determine the fire point is the same as that fordetermining the flash point. The fluid is heated and a flame passed overthe vapor of the fluid until the vapor is ignited and the fluidcontinues to burn.

To determine the autogenous ignition temperature, one ml. flask isimmersed into a molten lead bath. The temperature of the molten leadbath is continually measured with a thermometer. As the autogenousignition temperature is approached, one drop of the fluid is insertedinto the flask and the temperature at which spontaneous i nition takesplace is the autogenous ignition temperature. With the fluids of thepresent case the fire point is greater than 470 F. and the autogenousignition temperature is 800 F. or greater. As mentioned previously, thefire point and the autogenous ignition temperatures should be consideredin order to determine the probability of the brake fluid causing a fire.With the fluids of the present invention. because of their higher flashpoints and autogenous ignition temperatures, it is very unlikely thatthe brake fluid will burn or cause a fire in an automobile because ofleaks or a rupture in the brake fluid line.

The brake fluids of the present case have also been subiected to astandard fire test where 40 g. of the brake fluid are placed in a ml.beaker and the beaker then placed in a rotating stage oven which ismaintained at 500 F. With the glycol based fluids, after they have beeninserted into the rotating oven for 15 minutes, they burst into flamesand continue to burn. Even after the flames have been extinguished andthe fluid has again been expos d to oxygen. the glycol based fluids willimmediately ignite and continue to burn. When the fluids of the presentcase were subjected to the same test, the fluids survived 12 hours withsome vapor loss in the rotating stage oven which was maintained at 500F., thus showing that the fluids of the present case were considerablymore stable and non-combustible at high temperatures.

The kinematic viscosity test is a determination of the measure of thetime necessary for a fixed volume of the brake fluid to flow through acalibrated glass capillary viscosimeter under an accurately reproduciblehead and a closely controlled temperature. The kinematic viscosity isthen calculated from the measure of flow time and the calibrationconstant of the viscosimeter. At 40 C., the brake fluids of thisinvention have a viscosity of 600 to 1600 centistokes. At 212 F., thebrake fluids of the present case have a viscosity that exceeds that ofthe glycol based fluids.

In the pH value determination, a quantity of the brake fluid is dilutedwith an equal volume of a methanol-water solution. The pH of theresulting mixture is measured with a prescribed pH meter assembly at 23C. For all types of brake fluids, the brake fluids as tested must have apH of not less than 7 or more than 11.0. A mild base is added to thebrake fluids of the present invention such that as measured by the abovepH method, the pH of the fluid is 7.2 to 9.6. A mild base that can beadded to the fluids of the present case so that they will pass the pHstandard test is barium hydroxide.

The brake fluid stability test comprises a high tempera ture stabilitytest and a chemical stability test. In the case of the high temperaturestability test, a 60 mm. sample of the brake fluid is heated to anappropriate holding temperature, and then the brake fluid is maintainedat the holding temperature for 120:5 minutes. Then, for the next 5:2minutes, the fluid is heated to an equilibrium reflux'rate of 1 to 2drops per second and the temperature is taken. The fluids of the presentcase pass this test.

In the case of chemical stability, 30:1 ml. of the brake fluid is mixedwith 30:1 ml. of SAE 1' compatibility fluid in a boiling flask. First,the initial equilibrium reflux boiling point of the mixture isdetermined by applyng heat to the flask so that the fluid is refluxingat 10:2 minutes at a rate in excess of 1 drop per second.-.

11 Then over the next 15:1 minute, the reflux rate is adjusted andmaintained at 1 to 2 drops per second. This rate is maintained for anadditional 2 minutes and the average value is recorded as the finalequilibrium reflux boiling point. The brake fluids of the present casealso pass this test.

The corrosion test comprises polishing, cleaning and weighing 6specificed metal corrosion test strips and assembling them as prescribedin the standards. This assembly is placed on a standard rubber wheelcylinder cup in a corrosion test jar and immersed in the brake fluid,capped and placed in an oven at 100 C. for 120 hours. Upon removal andcooling, the strips and the fluid cup are examined and tested. The metaltest strips are observed to note whether pitting or etching arediscernible, whether there are any crystalline deposits which form andadhere to the glass jar Walls or the surface of the metal strips, andwhether there is sedimentation in the fluid water mixture. The metalstrips are weighed for weight loss and other determination are made withrespect to the test. The brake fluids of the present case pass this testwithout any difliculty.

Another test was carried out by the present inventor in order todetermine the chemical stability of the fluids of the present case ascompared to the glycol based fluids that are available on the market. Inthe test, 40 g. of each fluid was taken and placed in a 150 mm. beakerand placed in a rotating stage oven which was maintained at 400 F. Thehigh temperature glycol based fluids were 80% volatilized in hours. Theultra high temperature glycol based fluids were 30% volatilized in 5hours and the fluids of the present case were volatilized only 4% in thesame number of hours. In a 20-hour period, the high temperature glycolbased fluid was 85 to 87% volatilized. The ultra high temperature glycolbased fluid in 20 hours was 75% volatilized and the fluids of thepresent case were only 11% volatilized. These results indicate thethermal and chemical stability of the fluids of the present case, ascompared to the brake fluids presently on the market.

The fluidity and appearance at low temperature test comprises takingbrake fluid and lowering it to expected minimum exposure temperaturesuch as 40 C. and the fluid is then observed for clarity, gelation,sedimentation, excessive viscosity or thixotropicity. The brake fluid ofthe present invention usually absorbs from the atmosphere or throughosmosis in the hydraulic lines of a brake fluid system in an amount ofwater which is less than 0.5% by weight and usually less than 0.2% byweight of water. With this amount of water the brake fluid of thepresent case has no crystallization, cloudiness, stratification orsedimentation and upon reversion of the sample bottle in which the testis carried out, the time required for the air bubble to travel to thetop of the fluid is less than seconds.

In the evaporation test, 25 ml. of brake fluid is placed in a covereddish for 48 hours at 100 C. in an oven. It is then taken out and thenreturned to the oven for 24 hours at 100 C. and this is continued for atotal period of 7 days. The nonvolatile portion is measured and examinedfor residues. The residues are then combined and checked for fluidity at5 C. In the present case, there is only a loss of 2.5% by weight ofvolatiles after the 7 day period.

In the water tolerance test, the brake fluid is diluted with water andstored at low temperatures of 40 C. to -50 C. for 24 hours. The coldwater wet fluid is first examined for clarity, stratification andsedimentation and placed in an oven at 60 C. for 24 hours. On theremoval, it is again examined'for stratification and the volume percentof sedimentation by centrifuging. The brake fluid of the present case issubjected to this test with the amount of water that normally it wouldpick up from the atmosphere upon being exposed to the atmosphere for anextended period of time, which is usually 12 0.2% by weight of water.With this amount of water, the ester polysiloxane brake fluid of thepresent case passes this test.

In the compatibility test, a sample of the brake fluid is mixed with anequal volume of SAE 1 compatibility fluid, then tested in the same Wayas for water tolerance except that the bubble flow time is not measured.The test is an indication of the compatibility of the test fluid withother motor vehicle brake fluids at both high and low temperatures. Thepolysiloxane brake fluid of the present invention is fairly compatiblewith most standard brake fluids.

In the resistance to oxidation tests, the brake fluid is activated withapproximately 0.2% benzoyl peroxide and 5% water. A corrosion test stripassembly consisting of a cast iron and aluminum strips separated by tinfoil squares at each end are then rested in a piece of SBRWC cup so thatthe test strips are half immersed in the fluid and oven aged at 70 C.for 166 hours. At the end of this period, the metal strips are examinedfor pitting, etching and weight loss. The polysiloxane brake fluid ofthe present case, when it was subjected to this oxidation test, passedthe test without any difiiculty and there was no residue or depositsformed as the result of oxidation.

The next test is the effect on rubber where the four selected SASBRWCrubber cups are measured and their hardness determined. The cups, two toa jar, are immersed in the test brake fluid, one jar is heated for hoursat 70 C. and the other for 70 hours at 120 C. After the cups are washedand examined for disintegration, they are remeasured and their hardnessredetermined. The polysiloxane brake fluid of the present case passedthis test without any difliculty.

Another test is the stroking properties test. In this test, the brakefluid is stroked under controlled conditions at an elevated temperaturein a simulated motor vehicle hydraulic brake system consisting of 4slave wheel cylinders and a master cylinder connected by steel tubing.Standard parts are used. All parts are carefully cleaned, examined andcertain measurements made immediately prior to as-' sembly for test.During the test, the temperature, rate of pressure rise, maximumpressure and rate of stroke are used as specified. The system isexamined periodically during stroking to assure that excessive leakageof fluid is not occurring. Afterwards, the system is torn down, metalparts and rubber cups are examined and remeasured. The brake fluid andany resultant sludge and debris are collected, examined and tested. Thepolysiloxane brake fluid of the present case passed this test.

The polysiloxane brake fluid of the present case was also tested inaccordance with a Federal test on corrosive instability. Thepolysiloxane of the present case was put into a tube and then metalplates on a hanger were placed in a tube such .that they were coveredwith the fluid. A condenser was then placed above the tube and the tubewas heated to 200 P. so that reflux could take place and the tube washeated to 200 F. for 168 hours. Then the metal sample plates were takenout, wiped and checked for corrosion and the fluid was checked fordeposits or residue or stratification. The polysiloxane brake-fluid ofthe pres-.

ent case also passed this test without any difliculty.

The polysiloxane hydraulic fluids of the present casefar exceed thespecifications of the high temperature glycol based fluids and the ultrahigh glycol based fluids in terms of flash point, in the evaporationtest and thermal stability. Not only is the polysiloxane hydraulic fluidof the present invention more stable at high temperatures, it has a muchlower viscosity at low temperatures than that specified for the best lowtemperature glycol based fluid presently on the market. 7

Brake fluids may be prepared according to the present invention whichhas a viscosity of as low as '600 cs. at 40 C. The advantage of this isthat there is no sluggishness in the brakes at low temperatures. Itshould be understood that the polysiloxanes of this present case may beused in anyhydraulic system, including a brake hydraulic system.

Another advantage of the brake fluid of the present case is its lowwater hygroscopicity or pick-up from the atmosphere. In fact, thepolysiloxane brake fluid of the present invention can be said to repelwater rather than to attract it and add it to the polysiloxane mass. Infact, no more than 0.20 weight percent of water is picked up by thepolysiloxane brake fluid of the present case when the brake fluid isplaced in a standard brake hydraulic rubber hose which is immersed in awater bath over an extended period of time. The brake fluid of thepresent invention will pick up even less water from the atmosphere uponbeing exposed to a humid atmosphere for periods as long as one year ormore. With this amount of Water moisture, in fact with up to 0.5 weightpercent of the polysiloxane as water mixed in with the polysiloxanefluid, the polysiloxane of this case is operable as a brake fluid.

Brake fluids presently on the market, that is, glycol based brakefluids, are notoriously hygroscopic; such brake fluids will pick up fromthe air large amounts of water, which moisture may cause problems at lowtemperatures or may cause problems at high. temperatures such assluggish action of the brakes or rupture of the hydraulic brake lines.

The following examples are given below in order to better illustrate thepresent invention without intending to limit the invention. All partsare by weight.

equipped with mechanical stirrer, thermometer, Y-head addition funnel,condenser, and heating mantle, there is added 190 parts of To this thereis added 200 parts of dry toluene and this reaction mixture is heated to110 C. After the temperature has reached 110 C., a S-part fraction ofallylacetate from a total change of 79 parts of allylacetate is added.At this point, 0.1 cc. of 38,500 p.p.m. Pt catalyst solution was addedto initiate and perpetuate the SiH-olefin addition reaction. Thereaction vessel temperature was controlled between 110 C. to 120 C. bythe addition rate of allylacetate. After the final portion ofallylacetate was added to the reaction flask, the solution was agitatedfor one hour. The solvent and low boiling siloxanes were stripped off at200 C. and at 0.2 mm. pressure. The siloxane fluid was decolorized withcarbon black and fullers earth and then filtered through Celite 545 toyield a pale yellow liquid which has the chemical structure,

According to the equilibrium reflux boiling test, the above fluid has aboiling point of 430 F. with /2 weight percent water in it and it has aboling point of 340 F. with 1 weight percent Water. Viscositydetermination produced the following results:

Temperature, F.: Viscosity, cs. 67 1317 77 38.4 100 29.4 210 9.5

This fluid has an open cup flash point of 470 F.

14 EXAMPLE 2 i i (CH3)3S1O sliO] SiO:ISi (CH3);

CH3 6 I 3 and 200 parts of dry toluene. The reaction mixture is heatedto C., and 5 ml. portion of an allyl ester of methyl glycolic acid(hereafter referred to as the olefin) is added. Then 0.1 of 38,500p.p.m. Pt catalyst solution is added to initiate and perpetuate anSiH-olefin addition reaction. The pot temperature is regulated by theaddition rate of the olefin. After the final olefin portion was added tothe pot (total change 60 parts olefin), the solution is heated at C. andrapidly stirred for an additional period to insure completion.

Once the infrared scan of the mixture verifies the completion of thereaction, the solvent and low boiling siloxanes are stripped from thereaction at C. and 4 mm. The resulting siloxane fluid is decolorized andpolished, filtered with carbon black and fullers earth and then filteredthrough Celite 545.

The resultant fluid has the structure:

CH CHa CH3 CH3 CH3S iO- S iO SiiO S iCHS CH3 CH q 6H: CH3

C Hs 3 EXAMPLE 3 To a two liter three necked round bottomed flaskequipped with collection bead, mechanical stirrer, thermometer, Y-head,addition funnel, condenser and heating mantle, there is added 474 partsof,

and 500 parts of dry toluene. The solution is refluxed at 120 C. toazeotrope out any residual water prior to olefin additions. To thereaction mixture, which is heated at 110 C., a 10 m1. portion ofallylethylsuccinate (hereafter referred to as the olefin) is added.

To initiate the reaction 0.2 cc. of 45,000 p.p.m. of Pt catalystsolution is added. The heating source is stopped and a vigorous olefinaddition reaction is maintained by addition of the olefin, whose totalcharge is 295 parts.

Once the olefin is completely added the reaction vessel is warmed anadditional half-hour to insure completion of the SiH-olefin reaction.Upon completion of reaction, the fluid is stripped of low boilers at 192C. at 2 mm. and filtered through Celite #545.

The resultant siloxane fluid structure is:

CH CH3 CH3 EXAMPLE 4 There was added 857 parts of and 800 parts oftoluene to a three liter three necked round bottomed flask equipped witha mechanical stirrer, Y-head, thermometer, addition funnel, condenser,and heating mantle. The mixture is heated to 120 C. to azeotrope thetoluene-oil solution. After the solution is dried, 25 ml. ofallylethylacetoacetate (hereafter referred to as the olefin) is added.

A platinum catalyst solution (0.5 cc. of 20,000 p.p.m. Pt) is added andan exothermic reaction noted. The reaction mixture temperature iscontrolled at 120:10" C. by the addition rate of the olefin. The totalamount of the olefin added by weight is 550 parts.

Upon completion of the reaction, the solution is filtered throughfullers earth and then stripped to 185 C. at 3 The resultant fluid hasthe following structure:

CH3 CH3 (CH SiO- SiO O Si(CH.-4)3

EXAMPLE 5 To a 300 ml. three necked round bottomed flask equipped withcollection head, mechanical stirrer, thermometer, Y-head, additionfunnel, condenser, and heating mantle, there was added 80 parts of and80 parts of dry toluene. The solution is refluxed at 120 C. to azeotropeout any residual water. After azeotroping the solution, a 2 ml. portionof the allyl ester of 2 (2 methoxyethoxy)ethylglycolic acid (hereinafterreferred to as the olefin) is added to the reaction vessel.

An 0.05 cc. portion of 29,000 p.p.m. Pt catalyst solution is added tocatalyze the SiH-olefin addition. The reaction vessel temperature isregulated by the olefin addition rate. The reaction is rated to bemildly exothermic.

When the full 359 parts of olefin has been added, the reaction is warmedat C. for 2 hours to finalize the addition. The resultant siloxane fluidis stripped to 165 C. at 5 mm. to remove the boiling component andsolvent.

The compound has the structure EXAMPLE 6 To a 2-liter three necked roundbottomed flask equipped with a collection head, mechanical stirrer,thermometer, Y-head, addition funnel, condenser, and heating mantle,there is added 356 parts of,

i) CH3 CH3 CHaOCHzCHg-C-O-CH-CHz-CHaSiO Sio] 11 H3 CH3 EXAMPLE 7 To a5-liter three necked round bottomed flask equipped with a collectionhead, mechanical stirrer, thermometer, Y-head, additional funnel,condenser, and heating mantle, there is added 1500 parts of,

and 1000 parts of toluene. The solution is heated to C. and azeotropedto remove residual Water. Once the azeotrope is completed a 20 ml.portion of the 3-buten-1- o1 ester of acetic acid (henceforth referredto as the olefin) is added.

To initiate and perpetuate the olefin addition, an 0.3 cc. portion of42,500 p.p.m. 'Pt catalyst solution is added. The exothermic reaction iscontrolled by the rate of addition of the 700 parts of olefin. Thereaction temperature is maintained at 1001118 C. Once the addition ofthe olefin is completed the pot is heated at 120 C. for 3 hours toinsure complete reaction. The solution is stripped to 200 C. at 1.2 mm.and filtered through Celite #545.

The resultant siloxane compound has the structure:

CH3 CH3 (CHJ)3S0 S iO SiQ SKCHa);

CH3 2; H3

Ha 6H2 6:0 A... 4

EXAMPLE 8 To a 1000 ml. three necked round bottomed flask equipped witha mechanical stirrer, thermometer, Y-head, addition funnel, condenser,and heating mantle, 265 parts CH; CH2 (CHa)aSiO[ iO [ShO]Si(CH;)

and 300 parts of dry toluene are added. The reaction mixture is heatedto 110 C. and at 110 C., 6 ml. portion of allylacetylglycolate(hereinafter referred to as the olefin) is added.

A 0.125 cc. of 37,600 p.p.m. Pt catalyst solution is added to catalyzean SiH-olefin addition reaction. The 155 part of allylacetylglycolate isslowly added to the reaction solution. The rate of olefin addition tothe vessel is used to control the pot temperature at 120 C.i- C. Afterthe SiI-I-olefin reaction is completed, the resultant siloxane fluid isstripped to 193 C. at 1.5 mm. and filtered through fullers earth topolish the fluid.

The resultant fluid has the following structure:

EXAMPLE 9 The brake fluid of Example 1 is subjected to the tests setforth above in the specification for motor vehicle brake fluids. Theresults obtained from these tests as compared with the suggestedspecifications for brake fluids are set forth in Table 1 below:

TABLE 1.-TEST DATA FOR EXAMPLE 1 FLUID Example 1 Test Suggested spec.fluid E.R.B.P 446 F 525 F. Wet E.R.B.P 320 350 F. Flash point. 212 375F. Viscosity (40 CA 1,800 630. Viscosity C 1.5 cr- 4.5 cc.

Example 2 fluid pH. 7.11--- 7.2. High temperature stability 3.0 CNegligible. l stability 3.0 0 Do. Corrosion:

.2 mg. steel 0.013 mg. (a) Metal wt. loss (approx.) .1 mg. aluminum0.004 mg. .4 mg. brass, copper..- 0.104 mg. (1)) Appearance No ellin N0gelling. (c) Low temperature No gelling at 23=|=5 0... Do.

D pn it: None None. (e) Sedimen 0.1% 0.04%. (i) pH 7.11--- 7.11. (g),Rubber hardness 15 IRHD 15. (h) Rubber swell 0.55" 0.015 Fluid apearence at low temperature Example 2 fluid has less than 0.1 weightpercent water):

(a) Clarity Clear Clear Evaporation Residue N on-abrasive N one Residueflow pt..- 0 5 Corrosion test. Passed Oxidation test. Do. Strokiugproperties test Do.

What is claimed is: 1

1. A process for transmitting force in a hydraulic system fromactivating means to activated means in a hydraulic system having areservoir means wherein said activating means, said activated means andsaid reservoir means are connected by hydraulic line means and all ofsaid means are substantially 'filled with a polysiloxane comprisingapplying mechanical force to said activating means where saidpolysiloxane polymer has the structure,

where R is selected from the class consisting of alkyl radicals of lessthan 8 carbon atoms and phenyl, F is selected from n is a whole numberthat varies from 2 to 4 and z varies from 1 to 4, where a varies from1.11 to 2.02, b varies from 0.023 to 1.00 and the sum of a+b varies from2.024 to 3.00.

. 2. The process of-Claim 1 wherein R' is selected-from the classconsisting of alkylene, arylene radicals and hydrocarbon substitutedalkylene and arylene radicals of up to 20 carbon atoms and R, R and Rare alkyl radicals. 3. The process of Claim 1 wherein a varies from 1.23to 2.02, b varies from 0.055 to 0.92 and the sum of al-l-b varies from2.074 to 2.5.

4. The process of Claim 1 wherein the polymer has the structure,

has

the formula,

(CHa-i JO(CHa)a) (CHa):SiO (O'HaSiO) ((CHshSiCDm the formula,

[(CHn)a0 (z-(0mm 01131 References Cited UNITED STATES PATENTS 2/1969Deane 188-352 X 4/1973 Traver 25278 LEON D. ROSDOL, Primary Examiner H.A. PITLICK, Assistant Examiner US. Cl. X.R.

